The problem is that the lighter you make something the more
difficulty it has in withstanding the G forces of launch.
The rail gun approach seems better in this case since
it can keep the G forces down.

I do think either approach makes much more sense for
resupply pods. It also makes sense from a manufacturing
perspective (hurling up aluminium and silicon ingots).

The problem with the parabolic mirror approach to energy
production is that you have to keep the mirror focused
on the sun as it orbits around the Earth. That is going
to require propellant mass I believe. Spike could probably
tell us how much. Unless you are planning on attaching it
to the station and using a mechanical orientation device.
You also lose the sun half of the time so you are going
to need batteries.

The approach does make a lot more sense because you can
use much more of the energy spectrum of the sun than PV
cells do. You need conversion devices. NASA Glenn Research
Center is working on Stirling engines to accomplish this.

The numbers (at least for the solar panels) sound about
right to me.

I'll note that we will have 6 people on the station for
the next week or so. So we are going into space, just
very slowly.